- The potato is the top non-grain food crop in the world (following corn, wheat and rice) and the number one vegetable crop in the U.S.
- Native to South America, potatoes have been cultivated for many centuries and belong to the Solanaceae family.
- Potatoes are an important source of several nutrients, especially Vitamin C. A single medium sized potato provides nearly half the daily adult requirement (100 mg) of Vitamin C and it is also a source of Vitamin B6, niacin, and potassium.
- Pound for pound, potatoes are one of the best values in the produce section.
- In general, potatoes are a safe food to eat but mishandling prepared potato dishes, such as potato salad or foil-wrapped baked potatoes, may result in bacterial growth and cause illness.
The potato (Solanumtuberosum L) is a starchy, tuberous vegetable in the nightshade family, Solanaceae. Potatoes were introduced outside the Andes region four centuries ago, and have become the world’s most economically important and widely consumed vegetable. A tuber is any enlarged root or stem that stores nutrients for the plant and from which shoots will grow.
Potato flesh is a complex carbohydrate and the most affordable source of potassium in the produce department. Each year more than 1 million acres of potatoes are planted and 41.3 billion pounds are harvested, China has become the largest producer of potatoes worldwide. There are hundreds of types of potatoes sold in the United States which fit into seven categories: russet, yellow, red, blue/purple, white, fingerling, and petite. Each have their own unique taste, texture and appearance, making the preferred cooking methods different for each variety.
Reds: have a smooth, moist texture good for soups and stews because they maintain their shape once cut throughout cooking. ‘New’ potatoes are produced in the spring or early summer and have a waxy texture and a thin skin.
Russets: these are generally larger in size and make up most of the U.S. crop. These are good for baking, mashing and making gnocchi.
Yellows: have a golden flesh and creamy texture. Yukon Golds are famous for their yellow color and rich, starchy flavor.
Specialties: these include potatoes such as fingerlings, blue/purple (Purple Majesty and Mountain Rose). Their unusual color lends dishes an unusual appeal. Ideally used mashed, roasted or in salads.
In the 1840s a major plant disease outbreak caused by potato blight, an organism which can infect vegetables in the nightshade family, swept across Europe, killing most of the potato crops. This led to the Irish Potato Famine and disappearance of Europe’s primary food source, with almost one million people dying from starvation and disease. The first permanent U.S. potato crops were established in Londonderry, NH in 1719 and from there, they spread widely to the rest of the states. Today, Idaho, Washington, Wisconsin, North Dakota, and Colorado are the top potato producing states.
Regional information, Colorado:
Over 100 potato varieties are grown in Colorado with most production located in the San Luis Valley, at 7,600 feet this is one of the highest potato production areas on the world. In Colorado, potato harvest begins in September with about 98% of the crop going to storage before being shipped.
Food safety issues associated with potatoes often involve prepared dishes, such as potato and other deli-style salads, and baked potatoes. Potato salad was the likely source of a Salmonella gastroenteritis outbreak in 2009 (Mank et al. 2010) and a norovirus outbreak traced to an ill food handler (Chandler et al. 2000). Bacillus cereus poisoning has been associated with mashed potatoes (Palma 1985) and mashed potatoes made with raw milk was the suspected source of a Staphylococcus aureus outbreak in Norway (Jorgensen et al. 2005). Botulism has been linked to temperature abused potato salad (Brent et al. 1995) and a baked potato added to prison-made illicit alcohol was the suspected source of Clostridium botulinum spores in a botulism outbreak in 2011 (Thurston et al. 2012).
The potato is normally grown from “seed potatoes” which are small tubers or pieces of tuber sown to a depth of 5 to 10 cm. The planting density of a row of potatoes depends on the size of the tubers chosen, while the inter-row spacing must allow for ridging of the crop. Ridging (or “earthing up”) consists of mounding the soil from between the rows around the main stem of the potato plant. Ridging keeps the plants upright and the soil loose, prevents insect pests such a tuber moth from reaching the tubers; and helps prevent the growth of weeds.
The use of chemical fertilizer depends on the level of available soil nutrients and in irrigated commercial production, fertilizer requirements are relatively high. However, potatoes can benefit from application of organic manure at the start of a new rotation – it provides a good nutrient balance and maintains the structure to the soil. The soil moisture content must be maintained at a relatively high level. For best yields, a 120 to 150 day crop requires from 20 to 27.5 inches of water. Crop rotation, using pest tolerant varieties, and healthy, certified seed tubers are strategies used in avoiding crop losses. Insect pests can wreak havoc on a potato crop. Even damage caused by the Colorado Potato Beetle, a major pest, can be reduced by destroying beetles, eggs and larvae that appear early in the season, while sanitation, crop rotations and use of resistant potato varieties help prevent the spread of nematodes.
Yellowing of the potato plant’s leaves and easy separation of the tubers from their stolons indicate that the crop has reached maturity. If the potatoes are to be stored rather than consumed immediately, they are left in the soil to allow their skins to thicken – thick skins prevent storage diseases and shrinkage due to water loss. However, leaving tubers for too long in the ground increases their exposure to a fungal incrustation called black scurf.
Potato Storage and Handling
Since the newly harvested tubers are living tissue – and therefore subject to deterioration – proper storage is essential, both to prevent post-harvest losses of potatoes destined for fresh consumption or processing, and to guarantee an adequate supply of seed tubers for the next cropping season. For potatoes that will be processed, storage aims at preventing “greening” (the buildup of chlorophyll beneath the peel, which is associated with solanine, a potentially toxic alkaloid) and losses in weight and quality. The tubers should be kept at a temperature of 6 to 8°C degrees, in a dark, well-ventilated environment with high relative humidity (85 to 90 percent).
Potatoes should not be washed by consumers before storing; dampness promotes early spoilage. For home storage, potatoes should be stored in a well-ventilated cool, dry, and dark place, ideally between 45-55°F. Potatoes should not be stored at refrigerator temperatures because this can cause potato starches to convert to sugars, resulting in a sweeter taste and excessive darkening during cooking.
To contribute to the Potatoes Production section, please follow this link: http://fsi.colostate.edu/
Potatoes, as well as other vegetables in the nightshade family, can produce solanine, an alkaloid substance which causes potatoes to turn green and have a bitter flavor. Solanine is actually a defense mechanism against insects, disease, and predators. Potato leaves and stems contain this poison and should never be consumed. Solanine, in small doses is toxic and causes headaches, nausea, vomiting, diarrhea, and even paralysis of the central nervous system; in large doses it can be fatal. Potatoes can develop solanine if they have been exposed to light, especially florescent light, or extreme cold or warm temperatures for prolonged periods of time. If green discoloration is noticed on a potato, the green can be cut off and discarded. Sprouts are a sign that the potato is trying to grow. Storing potatoes in a cool, dry, dark location that is well ventilated will reduce sprouting. Sprouts should be cut away before cooking. Sometimes potatoes that are cut but uncooked take on a pinkish or brownish discoloration. This is due to the carbohydrate in the food reacting with oxygen in the air. Potatoes that become discolored are safe to eat and do not need to be discarded. The color usually disappears with cooking. Storing in cold water or adding lemon juice or vinegar to the water can inhibit discoloration. Soaking in water should be limited to two hours to retain water-soluble vitamins.
As with all fresh produce, hands should be washed before preparing potatoes. Potatoes should be washed well under running water and scrubbed with a clean vegetable brush before cooking or baking, peeling can remove the hard to clean outer surface. Prepared dishes should be stored properly to maintain a safe temperature.
Potato salad: it is best to cool down the cooked potatoes to 40°F BEFORE mixing in other ingredients. The prepared potato salad should be kept at refrigerated temperatures, 40°F or less, until ready to serve.
Baked potatoes: If heating baked potatoes in foil to serve at a later time, ensure that the potato cools quickly and is stored in the refrigerator until used. A thermometer should be used to verify potatoes are reheated to 140°F before serving.
Mashed potatoes should be prepared with pasteurized milk and kept at a proper temperature, above 140°F during serving or 40°F or less for storage.
Potatoes are sometimes accused of being fattening but by itself, a potato contains very little fat, generally listed as 0 grams of total fat per serving, and 26 grams of total carbohydrate. However, frying potatoes in oil or adding butter and sour cream can more than double the calories in a potato product. Another common misconception is that all of a potatoes’ nutrients are located in its skin. Approximately half of the dietary fiber is found within the potato itself. Potatoes are high in fiber, both soluble and insoluble, and contain anywhere from 3 to 7 grams of fiber, depending on their size. Potatoes contain significant amounts of iron, providing women with 25% and men with 57% of their recommended daily value; 88% of the total amount of iron in a baked potato is found in its skin.
It is beneficial to cook and eat potatoes with the skin, as that is where half of the potato’s fiber, much of its potassium, and other important nutrients are found. Potato skin contains Vitamins B and C, calcium and is rich in phytochemicals, which may help to protect the body from chronic diseases. As with many other vegetables, the method of cooking can affect the bioavailability of certain nutrients. Nutrient losses are greatest when boiling; water soluble vitamins and minerals will leach out into the cooking water. To maintain the highest nutrition of a cooked potato, steaming or microwaving are the best choices.
- Garden-Robinson, Julie, et al. Potatoes from garden to table. North Dakota State University, Fargo, North Dakota. May2012. http://www.ag.ndsu.edu/pubs/yf/foods/fn630.pdf
- Sheehan, Jan. “Healthy Eating.” Healthy Eating. Hearst Communications Inc, 2014.
- Alfaro, Danilo. “What Is Solanine? Or, Why Do Potatoes Turn Green?” About.com Culinary Arts. N.p., 2014.
- Mikkelson, Barbara, and David P. Mikkelson. “Snopes.com: Green Potatoes Poisonous?” Snopes.com: Green Potatoes Poisonous? Urban Legend Reference. Pages, 1995.
- “What Is a Tuber?” WiseGEEK. Conjecture Corporation.
- Campbell, Meg. “Healthy Eating.” Healthy Eating. Demand Media, 2014.
- Brent, J. et al. 1995. Botulism from potato salad. Dairy, Food and Environmental Sanitation. 15(7): 420-422.
- Chandler, B., et al. 2000. Outbreaks of Norwalk-like viral gastroenteritis – Alaska and Wisconsin, 1999. Morbidity and Mortality Weekly Report. 49(10): 207-211.
- Jorgensen, H. et al. 2005. An outbreak of staphylococcal food poisoning caused by enterotoxin H in mashed potato made with raw milk. FEMS Microbiology Letters 252: 267-272.
- Palma, A. 1985. Mashed potatoes and Bacillus cereus poisoning. Ristorazione Collettiva, 10 (3): 117-118.
- Thurston, D. et al. 2012. Botulism from drinking prison-made illicit alcohol – Utah 2011. Morbidity and Mortality Weekly Report. 61(39): 782-784.
- US Potato Board. ”Are Potatoes Healthy? Yes They Are!” Potato Goodness Unearthed. 18 Feb. 2014.
- FAO, The Potato.pdf (2008) (available at http://www.fao.org/potato-2008/en/potato/cultivation.html).
- International Year of the Potato 2008 (available at http://www.fao.org/potato-2008/en/index.html).